ES2652517B1 - EXCHANGER FOR WIND TUNNEL - Google Patents

Description

DESCRIPTION

Exchanger for wind tunnel

Object of the invention

The present invention relates to a system for exchanging heat with the air flow inside a wind tunnel, as well as to a method of regulating the temperature of the air flow inside a wind tunnel and design of said exchanger. In the interior of a wind tunnel it is necessary to cool the air flow and control the temperature of said air flow.

BACKGROUND OF THE INVENTION

The heat exchangers are used in wind tunnels, both horizontal and vertical, for the cooling of the air flow, which increases the temperature thereof due to the friction between said air flow and the inner walls of the wind tunnel duct.

It is important in these wind tunnels to maintain a constant temperature and air density, which is why it is necessary to control the temperature of the air flow. This involves achieving a uniform temperature profile in the test chamber or tunnel flight.

For this, passive air exchange systems are known, which expel hot air from the interior of the tunnel and replace it with new air, so that heat is dissipated from the interior of the tunnel. This new air is introduced through a system of gates with various designs. This method does not allow exhaustive control of the temperature of the air flow inside the tunnel.

On the other hand, heat exchangers are known inside the duct, similar to the water radiators used in the cooling of the automobile engine, which cool the air flow. These devices introduce high pressure losses in the air flow as the heat transfer area is increased.

Aerodynamic profiles installed in the curvatures or corners of the wind tunnel are also used, which allow obtaining a better flow profile with the corresponding introduction of some pressure loss. This system requires, for adequate cooling, the inclusion, inside said profiles, of a system designed to act as a heat exchanger.

Finally, there are also options for cooling the interior of the wind tunnel by spraying water or geothermal energy of low depth, which does not allow an optimal regulation of the temperature profile of the air flow and is not applicable in all types of systems , may also have undesirable negative effects such as excessive increase in relative humidity in the air inside the tunnel.

Description of the invention

The present invention proposes a solution to the above problems by means of a heat exchanger according to claim 1, a wind tunnel according to claim 14, a method of temperature regulation of an air flow inside a wind tunnel according to claim 15 and a design method for designing an exchanger according to claim 16. The dependent claims define preferred embodiments of the invention.

A first inventive aspect provides a heat exchanger for wind tunnels, comprising:

- at least one first wall and a second wall, each wall comprising at least one first edge, a second edge, a third edge and a fourth edge,

- a total number (N) of tubes (Tijk) adapted to contain a working fluid, at least a plurality of said tubes (Tijk) forming at least one series (Sj), where nS is the total number of series (Sj),

- at least one inlet manifold of the working fluid connected to a first end of at least one tube (Tijk), and

- at least one outlet manifold of the working fluid connected to a second end of at least one tube (Tijk),

wherein the tubes (Tijk) of each series (Sj) form a plurality (nFj) of rows (Fj) and a plurality (ncjf) of columns (Cj) distributed according to rows (Fj), and where:

- the distance (DTjf) between tubes (Tijk) of different rows (Fj) of the same series (Sj),

- the distance (DL1jfl) between tubes (Tijk) of the same row (Fj) and of different columns (Cj) of the same series (Sj),

- the distance (DL2jf) between tubes (Tijk) of different rows (Fj) and the same column (Cj), said column (Cj) being the closest either to the third edge or to the fourth edge, with respect to the tube ( Tijk) of the same series (Sj) closest to said third edge or fourth edge,

- the distance (DGj),

^or between the nearest tubes (Tijk) of adjacent series (Sj), or

^or between the tube (Tijk) closest to the first edge or second edge and said first edge or second edge of the heat exchanger,

they are parameterized so that:

- distance (DL2jf)> 0, and

- distance (DGj)> distance (DTjf),

so that:

- the parameterization relative to the rows (Fj) optimizes mainly the loss of pressure of the heat exchanger, and

- the parameterization relative to the columns (Cj) optimizes mainly the total effective transfer area of the heat exchanger.

Throughout this document, it will be understood that the heat exchanger is comprised between at least two walls, among which are the total number (N) of tubes (Tijk) of the heat exchanger. Said exchanger is, by means of these walls, partially limited in volume, so that preferably the volume defined by said walls is also defined by the dimensions of the wind tunnel. In this way, the air flow completely affects the total number (N) of tubes (Tijk) of the heat exchanger.

Advantageously, the section of the wind tunnel is completely occupied by tubes (Tijk) of the heat exchanger, so that there is an increased area of heat transfer with the air flow, without obstacles in the path of said air flow except the tubes themselves (Tijk).

Said tubes (Tijk) of the heat exchanger contain a working fluid, preferably a coolant, which circulates through the tubes (Tijk) allowing the transfer of heat between said tubes (Tijk) and the air flow outside these tubes ( Tijk).

In a particular embodiment, the working fluid may be either gaseous or liquid or solid.

Said working fluid allows, in a heat exchanger, both cooling and heating of the air flow, or any other fluid, circulating on the outside of the tubes (Tijk) of said heat exchanger.

Throughout this document, it will be understood that a series (Sj) is a set of tubes (Tijk), which in turn form a number of rows (Fj) and columns (Cj), which can be both variable and constant between the different series.

Advantageously, the distribution of the tubes (Tijk) in rows (Fj) and columns (Cj) in the heat exchanger, following a distribution established by the parameters DTjf, DL1jfl, DL2jf and DGj, allows an exchange of thermal power in the exchanger of heat with a minimum pressure loss.

The distances DTjf and DGj are considered as transverse distances in a particular embodiment, while DL1jfl and DL2jf are longitudinal distances.

The determination of the parameters allows an optimal heat transfer in the heat exchanger, since an excessively low value of the DTjf parameter causes a high separation of the air flow that impinges on the tubes (Tijk), so that it loses a large part of the effective thermal transfer area, whereas if the value of said parameter is excessively high, a high pressure loss occurs in the heat exchanger.

In addition, the determination of the parameter DL2jf allows reducing the separation of the air flow, allowing said air flow to flow between the different rows (Fj) of each series (Sj).

Additionally, an excessively low value of the parameter DL1jfl causes a reduction of the thermal transfer area of the heat exchanger.

Finally, the determination of the parameter DGj allows an optimum maintenance of the total number (N) of tubes (Tijk) of the heat exchanger.

In a particular embodiment, the value of the parameter DGj between consecutive series (Sj) allows access to each of the tubes (Tijk) of an operator or maintenance unit.

Advantageously, the determination of each of the different parameters allows the improvement of the characteristics of the heat exchanger. Additionally, the design of these combined parameters in the heat exchanger allows an optimal heat exchange with the air flow.

The correct parameterization relative to the rows (Fj) makes it possible to optimize mainly the velocity profile of the air flow at the outlet of the heat exchanger, while the correct parameterization relative to the columns (Cj) allows to optimize mainly the temperature profile of said air flow also at the outlet of the heat exchanger.

In a particular embodiment, the heat exchanger comprises at least two tubes (Tijk) in fluidic communication forming at least one coil (Ri).

A serpentine (Ri) is understood as a union of tubes (Tijk) through which the working fluid can circulate continuously.

This allows the flow of working fluid continuously between different tubes (Tijk) of the heat exchanger, so that the connections of the tubes (Tijk) are reduced both with at least one inlet manifold and with at least one manifold exit.

In a particular embodiment, the heat exchanger comprises a plurality (ni) of coils (Ri), where:

- each coil (Ri) comprises a plurality (g) of groups (Gj), and

- each group (Gj) comprises a plurality (ng) of tubes (Tijk),

where each series (Sj) is formed by the same group (Gj) of each coil (Ri), and where:

- the number (nFj) of rows (Fj) of each series (Sj) is the number of tubes (Tijk) comprising each group (Gj), and

- the number (ncjf) of columns (Cj) of each series (Sj) is the number of coils (Ri).

This distribution of tubes (Tijk) in the heat exchanger allows, advantageously, a tube connection (Tijk), preferably correlative, so that the temperature profile of the working fluid allows a homogeneous heat transfer with the air flow .

In a particular embodiment, the number (ng) of tubes (Tijk) of each group (Gj) is two or three tubes (Tijk).

This allows an optimal distribution of the total number (N) of tubes (Tijk) in the heat exchanger, as well as an optimal ratio of the parameters DTjf, DL1jfl, DL2jf and DGj.

In a particular embodiment, at least one tube (Tijk) does not allow the circulation of working fluid.

In a particular embodiment, at least one coil (Ri) does not allow the circulation of working fluid.

This allows, advantageously, a modular heat exchanger, in which the number of coils (Ri) or tubes (Tijk) operative during the operation of said heat exchanger according to the required specifications can be modified.

In a particular embodiment, the total number (N) of tubes (Tijk) of the heat exchanger fulfills the following expression:

In this way, the number of tubes (Tijk) is obtained according to an expression that depends on the number of rows (Fj), the number of columns (Cj) and the number of series (ns) of the heat exchanger, taking into account each one of the series (Sj), thus allowing to obtain a heat exchanger with a profile of speeds and a more uniform temperature profile at its output, with less loss of pressure.

In a particular embodiment, the total number (N) of tubes (Tijk) of the heat exchanger fulfills the following expression:

N = g. nj. ng

In this way, the number of tubes (Tijk) is obtained according to an expression that depends on both the number of rows (Fj) and the number of columns (Cj) of the heat exchanger, taking into account each of the series (Sj) .

Said number of tubes, arranged according to groups with the same number of tubes in equal coils, allows obtaining a profile of speeds and a more uniform temperature profile at the outlet of the heat exchanger, with a lower loss of pressure. In a particular embodiment, the total number (N) of tubes (Tijk) of the heat exchanger is obtained from the following expression:

^ A = Z and N jm = P F ^ t A ubom>

A being the effective total thermal transfer area of the heat exchanger, F m a thermal transfer factor that allows to take into account that the tunnel air flow does not completely wet the total area of each tube, due to the actual separation of said tube. flow, and A tube m the total thermal transfer area of a tube (Tijk).

Advantageously, the total effective area of heat transfer of the exchanger according to the number of tubes obtained thus has a value equal to or greater than the value of the total effective transfer area required for the design of said heat exchanger.

In a particular embodiment, the heat exchanger comprises a distance DL3jn, which is the distance from the third edge or fourth edge to the tube (Tijk) closest to each series (Sj), this distance preferably being the minimum distance established by construction of the heat exchanger.

This minimum distance is established according to manufacturability criteria of the heat exchanger.

Advantageously, the introduction of parameter DL3jn allows a correct manufacture, transport and / or installation of the heat exchanger, so that the tubes (Tijk) can not be damaged during the process and the space available for the installation of said tubes (Tijk) in the heat exchanger is the maximum.

In a particular embodiment, the parameterized distances DTjf, DL1jfl, DL2jf, DL3jn and DGj of the heat exchanger fulfill the following expressions according to the width (B) and the length (L) of the heat exchanger:

For the dimensioning of the heat exchanger, the maximum value of the values obtained in each case for the parameter Ljf, corresponding to each of the rows (Fj) of the same series (Sj), is taken for each of the series (Sj) Said maximum value allows, advantageously, to consider the maximum value of the sum of the different values of the parameters DL1jfl and DL2jf from those obtained for all the rows (Fj) of the same series (Sj), and for each of the series (Sj).

Advantageously, these relationships make it possible to obtain a heat exchanger that has minimal pressure loss and maximum heat transfer.

In a particular embodiment, at least one of the parameterized distances DTjf, DL1jfl, DL2jf, DL3jn and DGj of the heat exchanger maintains a constant value.

This allows a more uniform distribution of the tubes (T ^ijk ) in the heat exchanger the more constant the values of the different parameters.

In a particular embodiment, all parameterized distances DT ^jf are equal, all parameterized distances DG ^j between tubes (T ^ijk ) are equal and the number (n ^Fj ) of rows (F ^j ) of each series (S ^j ) is equal in the heat exchanger, and the expression is fulfilled:

B = ( ns ^one ) DGj ns ( nFj - l) DTJf

Advantageously, this allows a more uniform distribution of the tubes (T ^ijk ) in the heat exchanger and a simpler manufacture thereof.

In a particular embodiment, all the parameterized distances DL1 ^jfl are equal, all the parameterized distances DL3 ^jn are equal, the number (n ^Fj ) of rows (F ^j ) of each series (S ^j ) is equal and the number (n ^cjf ) of columns (C ^j ) of each series (S ^j ) is equal, and the expression is fulfilled:

Advantageously, this allows a more uniform distribution of the tubes (T ^ijk ) in the heat exchanger and a simpler and less expensive manufacture thereof.

In a particular embodiment, the heat exchanger comprises two inlet manifolds and two outlet manifolds, in which each of the coils (R ⁱ ) is connected alternately to a different inlet manifold and a different outlet manifold, so that the path of the working fluid has a sense that alternates in each coil (R ⁱ ).

In this way, each adjacent coil (R ⁱ ) alternates with respect to the direction of circulation of the working fluid.

This allows, in an advantageous way, a more homogeneous distribution of the workflow along the heat exchanger, by means of the different coils (R ⁱ ), which allows a heat exchange with the most homogeneous air flow, and therefore a profile of temperatures also more homogeneous.

Additionally, this allows an increased modularity of the heat exchanger, allowing the closure of certain coils (Ri) by means of any type of closure means to operate only with certain coils (Ri) of the heat exchanger, in case of leaks in some of them or in case of thermal transfer needs lower than the maximum that can be achieved with the exchanger.

In a particular embodiment, the closing means allow the closing of at least one tube (Tijk), allowing the closure of said tube for maintenance work or in case of thermal transfer needs less than the maximum that can be achieved with the exchanger.

In a particular embodiment, in the heat exchanger each tube (Tijk) is a circular tube (Tijk) with equal outside diameter (0).

The cross section of the tube (Tijk) is determined by the permissible range of working fluid velocities. The determination of the inner diameter of said tube (Tijk) is therefore also determined by the permissible range of working fluid velocities when this tube (Tijk) is circular. Finally, the outer diameter of said tube (Tijk) is determined by criteria of maximum pressure that said tube (Tijk) must hold or other structural or manufacturability criteria of the heat exchanger.

Advantageously, the heat exchanger is manufactured with commercial elements, preferably circular tubes, which allows a reduction of the manufacturing cost.

In a particular embodiment, the total effective heat transfer area of the heat exchanger, with all the tubes (Tijk) being circular, is as follows:

A = n0FHN

where F is an average thermal transfer factor for all tubes (Tijk).

In a second inventive aspect, the invention provides a wind tunnel comprising at least one heat exchanger as that of the first inventive aspect.

This allows the flow of air circulating along a wind tunnel to maintain a uniform temperature profile without distorting its profile of low velocity and pressure losses.

In a third inventive aspect, the invention provides a method of temperature regulation of an air flow inside a wind tunnel comprising the following steps:

- providing at least one heat exchanger according to the first inventive aspect,

- measure the temperature of the air flow inside the wind tunnel,

- regulate the temperature of the air flow by modifying either the number of tubes (Tijk) operative of the heat exchanger by means of closing means, or the conditions of the working fluid, or the parameterized distances DTjf, DL1jfl, DL2jf, and DGj.

Said modifiable working fluid conditions can be either the temperature, or the composition or the physical state of said fluid.

The regulation by means of the modification of parameterized distances comprises both the modification of the distances during the design of the system and the physical modification of the arrangement of at least one tube (Tijk) once all the tubes (Tijk) have been installed.

The temperature regulation of a wind tunnel airflow allows the control of both the temperature and the density of said air flow, so that both the test and flight conditions inside the wind tunnel are homogeneous and most adjusted to the corresponding real situation.

In a particular embodiment, the step of regulating the temperature of the air flow is carried out by modifying the parameterized distances DTjf, DL1jfl, DL2jf, DL3jn and DGj.

In a fourth inventive aspect, the invention provides a method of designing a heat exchanger according to the first inventive aspect for a wind tunnel comprising the following steps:

- defining the dimensions of the heat exchanger, said dimensions being width (B), height (H) and length (L),

- determine the total effective area (A) of heat transfer of the necessary heat exchanger as well as the thermal transfer factor (Fm) and the total area (Atubo m) of thermal transfer, of each tube (Tijk),

- determine the total number (N) of tubes (Tijk) of the heat exchanger by the following expression:

^a _™ _ Y _¿j w _{m = lr} ^F _mn ^A _{^ tubom} >

- determine the total number (n ^S ) of series (S ^j ), the total number (n ^Fj ) of rows (F ^j ) of each series (S ^j ), and the total number (n ^Cjf ) of columns (C) ^j ) of each series (S ^j ),

- determine the following parameters:

^or the distance (DT ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) of the same series (S ^j ),

^or the distance (DL1 ^jfl ) between tubes (T ^ijk ) of the same row (F ^j ) and of different columns (C ^j ) of the same series (S ^j ),

^or the distance (DL2 ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) and the same column (C ^j ), said column (C ^j ) being the closest either to the third edge or to the fourth edge, with respect to the tube (T ^ijk ) of the same series (S ^j ) closest to said third edge or fourth edge,

^or the distance (DG ^j ),

■ between the tubes (T ^ijk ) closest to adjacent series (S ^j ), or

■ between the tube (T ^ijk ) closest to the first edge or second edge and said first edge or second edge of the heat exchanger,

^or the distance (DL3 ^jn ) of the third edge or fourth edge to the nearest tube (T ^ijk ) of each series (Sj)

according to the following expressions:

The total area (Atubo m) of thermal transfer of a tube (Tijk) is defined according to the section of each tube, as well as the total number (N) of tubes (Tijk).

Additionally, once the determination step of the parameters specified according to the previous relations has been carried out, the correct determination of the total number (N) of tubes (Tijk) is checked by means of the expression:

Advantageously, the determination of the parameters DTjf, DL1jfl, DL2jf, DL3jn, DGj, nS, nFj and nCjf allows the design of an heat exchanger of optimum thermal transfer that has the air flow from the interior of the wind tunnel and low loss of Pressure.

In a particular embodiment, the design method further comprises the step of determining the total number (nl) of coils (Ri), the number (g) of groups (Gj) and the number (ng) of tubes (Tijk) in each group (Gj), prior to the stage of determining the different parameters DTjf, DL1jfl, DL2jf, DL3jn and DGj.

This allows, advantageously, a more uniform distribution of the tubes (Tijk) in the heat exchanger and a simpler and less expensive manufacture thereof.

All features and / or method steps described herein (including claims, description and drawings) can be combined in any combination, except combinations of such mutually exclusive features.

Description of the drawings

The foregoing and other features and advantages of the invention will be more clearly apparent from the following detailed description of a preferred embodiment, given solely by way of illustrative and non-limiting example, with reference to the attached figures.

Figure 1 shows a perspective view of an embodiment of the heat exchanger.

Figure 2A shows a front view of an embodiment of the heat exchanger.

Figure 2B shows a plan view of the cut A-A of Figure 2A.

Figure 2C shows a detailed view of Figure 2B.

Figure 3 shows a front view of an embodiment of the heat exchanger.

Figure 4 shows a diagram of the arrangement of an embodiment of the heat exchanger inside the wind tunnel.

Figures 5A and 5B show the comparison of the contours of temperature profiles of the fluid in the heat exchangers under test.

Figures 6A and 6B show the comparison of the contours of fluid velocity profiles in the heat exchangers under test.

Detailed description of a preferred embodiment of the invention

In the following detailed description the following nomenclature will be used:

- Coil: Ri

- Group: Gj

- Series: Sj

- Tube: Tijk

- Total number of coils: neither

- Total number of groups: g

- Number of tubes per group: ng

- Rows: Fj

- Columns: Cj

- Total number of rows (Fj) in each series (Sj): nFj

- Total number of columns in each series (Sj) distributed according to rows (Fj): ncjf

- Total number of series: nS

Figure 1 shows a heat exchanger (1) according to a particular embodiment of the invention, intended for installation in a wind tunnel (2).

Said heat exchanger (1) comprises a first wall (3) as a bottom wall and a second wall (4) as an upper wall. The flow of air to be cooled, coming from the wind tunnel (2), enters the heat exchanger (1) according to the direction shown in figure 1, that is, from the edge (9) of the heat exchanger (1) towards the edge (10) of the heat exchanger (1).

In this embodiment, the number (nl) of coils (Ri) is 55, each of said coils (Ri) comprising a total (g) of 6 groups (Gj), and each of these groups (Gj) comprising a number (ng) of 3 tubes (Tijk).

Said tube arrangement (Tijk) forms a total of 6 series (Sj), each of said series (Sj) comprising a total (nFj) of 3 rows (Fj), the number of rows (Fj) being the number (ng) ) of tubes (Tijk) of each group (Gj), and also comprising a total (ncjf) of 55 columns (Cj), said number of columns (Cj) being the number (nl) of coils (Ri).

The total number (N) of tubes (Tijk) in this particular example is 990 tubes, according to the described arrangement.

The value of the parameters N, nFj, ng, ncjf, Fj, Sj, Gj, Cj, nl are always integer values.

Said tubes (Tijk) have all cylindrical section, with an outer diameter of 28mm in this particular example.

The heat exchanger (1) also comprises two inlet manifolds (5) and two outlet manifolds (6), which are connected alternately to each of the coils (Ri). In this way, the odd coils (Ri) are connected to the input manifold (5) located to the left of figure 1, and to the output manifold (6) located to the right of figure 1, while the coils (Ri) pairs are connected to the remaining input (5) and output (6) collectors.

The working fluid circulates inside the coils (Ri) and accesses said coil (Ri) through the input manifolds (5) and leaves the coil (Ri) through the outlet manifold (6).

According to said connection arrangement of the coils (Ri) to the inlet (5) and outlet (6) collectors, an alternate path of the working fluid is obtained through the even and odd coils (Ri).

Figure 2A shows a front view of an embodiment of a heat exchanger (1), limited by a first wall (3) as a bottom wall and a second wall (4) as an upper wall, said walls (3, 4) defining the height (H) of the heat exchanger (1).

In this particular embodiment, said height (H) has a value of 3 m.

In this figure we can see the first coil (Ri) of the heat exchanger (1), formed by tubes (Tijk) joined together by means of bends. These elbows allow fluid communication between both tubes (Tijk) of the same group (Gj) and between groups (Gj).

These elbows are outside the air flow, being located outside the walls (3, 4) of the heat exchanger. This also occurs with the input manifolds (5) and the outlet manifolds (6). This allows the flow of air to find no obstacles in its path, except for the tubes (Tijk), so that the loss of pressure is minimized.

Figure 2B shows a plan view of the cut A-A made on the front view of Figure 2A.

Said plan view shows the remaining dimensions of the heat exchanger (1), that is, its width (B) and its length (L). In this particular embodiment, the width (B) has a value of 6 m and the length (L) has a value of 3.5 m.

Figure 2B also shows the arrangement of the 55 coils (Ri) and the 6 series (Sj) they form. In each of the series (Sj) the different groups (Gj) are also observed, which make up this series (Sj). As it is observed, a series (Sj) is the grouping of the same group (Gj) of each serpentine (Ri). For example, the series (S1) is the set of groups (G1) of the 55 coils that make up the heat exchanger (1).

The arrangement of each tube (Tijk) as a function of the row (Fj) and column (Cj) to which it belongs is also shown in Figure 2B, where the disposition between different series (Sj) and the displaced distribution of rows (Fj) and columns (Cj), according to a parameterization that is detailed below.

Figure 2C shows a detail (C), taken from the plan view of the section of Figure 2B.

This particular embodiment shows the different parameters that define the distribution of the tubes (Tijk) in the heat exchanger.

First, this detail partially shows two series (Sj), the series S5 and S6 in this embodiment, and the different groups (Gj) in each of them. Each series (Sj) is formed by 3 rows (Fj) and in which a maximum of 10 columns (Cj) are shown.

The parameters dimensioned in this particular embodiment are DTjf, DL1jfl, DL2jf and DGj, all of them being constants between different series (Sj), with the exception of the values of DL2jf in each series (Sj), which takes a zero value for the odd rows of each series (F1 and F3) and a constant value for the even rows (F2).

First, DTjf defines the distance between two rows (Fj) of the same series (Sj).

In this particular example, said distance has a value of 112 mm, so that it allows the access of an operator or machine for maintenance work of each of the tubes (Tijk) of the even rows (F2) of each series (Sj). ). This distance also allows the formation of a longitudinal duct, that is, in the direction of passage of the air flow, for the passage of said air flow.

The distance DL1jfl defines the distance between two tubes (Tijk) of the same row (Fj), said two tubes (Tijk) of the same row (Fj) always perfectly aligned. The value of the distance DL1jfl is 59 mm in this particular embodiment.

This distance allows the flow of incident air in both tubes (Tijk) to follow a suitable trajectory for a better use of the thermal transfer area of the tube (Tijk) located behind the previous one.

The distance DL2jf defines the distance between two tubes (Tijk) of two different rows (Fj) and the same column (Cj), said column (Cj) being closest to the third edge (9), with respect to the tube (Tijk) ) of the same series (Sj) closest to said third edge (9). Although in Figure 2C the columns (Cj) are displaced, they correspond one by one. Figure 2B shows the arrangement of a column, that is, a coil (Ri). The value of the distance DL2jf is 0 mm for the odd rows (F1 and F3) and 84 mm for the even rows (F2) in this particular embodiment.

This distance allows the flow of air to impact on a greater surface of tubes (Tijk), reducing the separation of the flow, so that it increases the heat transfer and decreases the pressure loss of the exchanger (1).

The distance DGj defines the distance between the two tubes (Tijk) closest to two consecutive series (Sj). The distance DGj also defines the distance between the tubes (Tijk) of the rows (Fj) located at the ends of the distribution of the total number (N) of tubes (Tijk) and the edges (7, 8) of the exchanger (1). ), located on the left and right of Figures 2B and 2C. The value of the distance DGj is 665 mm in this particular embodiment.

This distance allows both the access of an operator or machine as the free movement of these for maintenance work of each of the tubes (Tijk) of the odd rows (F1 and F3) of each series (Sj). This distance also allows the formation of a longitudinal duct, that is, in the direction of passage of the air flow, for the passage of said flow of air. air.

In a particular embodiment, the parameter DL3jn is also dimensioned.

Said distance DL3jn defines the distance between the edges (9, 10) of the heat exchanger (1) and the tube (Tijk) closest in each case.

This distance is taken during the parameterization, usually as the minimum distance necessary for the correct construction and manufacture of the heat exchanger (1). In this particular embodiment the DL3jn takes a value of 115 mm.

Figure 3 shows a front view of the particular embodiment of heat exchanger (1) described in the previous figures.

The situation of the lower and upper walls (3, 4) and one of the coils (Ri), connected to the inlet manifold (5) and to the outlet manifold (6), can be seen in this figure.

The figure also shows the connection between the different tubes (Tijk) that make up the coil, by means of bends, and the parameterization related to the ducts that allow the passage of air flow as well as the maintenance of each tube (Tijk) both by an operator as by a machine adapted for this purpose.

Finally, figure 4 shows a diagram of a wind tunnel (2) through which an air flow circulates. A heat exchanger (1) in said wind tunnel (2) is represented, already installed.

It can be seen how, in the operative position, the heat exchanger (1) has fluidic connections between the tubes (Tijk) and the inlet manifolds (5) and the outlet manifolds (6) located outside the real wind tunnel conduit (2) through which the air flow circulates.

Tests and simulations

In order to demonstrate the importance of the parameterization of the mentioned variables (DTjf, DL1jfl, DL2jf, DL3jn, DGj, nS, nFj and nCjf), especially the influence of the parameters DTjf, DL2jf, and DGj on the performance of the exchanger of heat, several Tests and simulations to compare the performance results of different heat exchangers by varying the values of these parameters.

These tests and simulations have been carried out with computational fluid dynamics software (CFD), and consist of comparing the pressure losses and temperature drops of the heat exchangers studied, in order to establish the differences in performance and behavior of said heat exchangers depending on the values given to the different parameters already mentioned; that is, the parameters DTjf, DGj and DL2jf.

Two different heat exchangers with different values of such parameters have been studied.

The first heat exchanger (IC1) is the one disclosed in the preferred embodiment already described, with the given parameter values, while the second heat exchanger (IC2) corresponds to a known heat exchanger with a classical distribution of tubes , wherein said tubes are arranged as a bundle of aligned tubes, having equal longitudinal distances and equal transverse distances between tubes. The values of the parameters of both heat exchangers are the following:

Two different comparisons have been tested and are shown in Figures 5a, 5b, 6a and 6b. For both cases, the air flow enters the heat exchanger from the upper part of the figures and leaves said heat exchanger from the lower part of said figures.

Figures 5A and 5B show the contours of temperature profile of the fluid in the heat exchangers under test. Results of the temperature evolution of the IC1 fluid in FIG. 5A can be observed, in which there is a wake of fluid cooled at the outlet of the heat exchanger, more intense than that observed for IC2 in FIG. 5B, decreasing the temperature of Average output. Accordingly, the heat transfer is higher for IC1, which demonstrates that the parameter conditions given in the preferred embodiment improve the efficiency of the heat exchanger. known heat IC2.

Figures 6A and 6B show the profile contours of fluid velocities in the same heat exchangers under test. Results of the fluid velocity distribution of IC1 can be seen in Figure 6A, in which the wake of the flow for each of the two sets of tubes is slightly wider than that shown for each of the six sets of tubes. IC2, which can be seen in Figure 6B, which indicates a higher pressure loss for this area in the distribution with two sets of tubes (IC1). These two sets of tubes can potentially result in higher local pressure losses than the equally spaced tubes in the IC2 distribution. However, due to the parameterization made in IC1, related to the values of DG, DT and DL2, the local pressure losses in the conduits in which DG is measured will be considerably lower for IC1. Consequently, a distribution of tubes of this type as provided in IC1 may result in higher local pressure losses in the regions affected by the wake of the flow, but at a lower overall pressure loss, demonstrating that the conditions of parameters given in this example (ie, in the present invention) improve the performance of a heat exchanger.

The following table also presents the results obtained from the simulations of CFD in the system per unit:

Pressure losses

Heat exchanger Temperature drop [p.u.]

[p.u.]

IC1 0.93 1.09

IC2 1 1

As shown in the table, IC1, that is, the heat exchanger of the preferred embodiment, has lower pressure losses while improving its temperature drop, thereby improving the performance of the heat exchanger.

Accordingly, the parameterization of a heat exchanger according to the first inventive aspect provides a heat exchanger in which the heat exchange with the fluid is higher, while at the same time resulting in lower pressure losses.

Additional remarks

The present invention is also directed to:

[1] Heat exchanger (1) for wind tunnels (2), comprising:

- at least one first wall (3) and a second wall (4), each wall (3, 4) comprising at least one first edge (7), a second edge (8), a third edge (9) and a fourth edge (10),

- a total number (N) of tubes (T ^ijk ) adapted to contain a working fluid, forming at least a plurality of said tubes (T ^ijk ) at least one series (S ^j ), the total number being (n ^S ) of series (S ^j ),

- at least one inlet manifold (5) of the working fluid connected to a first end of at least one tube (T ^ijk ), and

- at least one outlet manifold (6) of the working fluid connected to a second end of at least one tube (T ^ijk ),

wherein the tubes (T ^ijk ) of each series (S ^j ) form a plurality (n ^Fj ) of rows (F ^j ) and a plurality (n ^cjf ) of columns (C ^j ) distributed according to the rows (F ^j ), and where:

- the distance (DT ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) of the same series (S ^j ),

- the distance (DL1 ^jfl ) between tubes (T ^ijk ) of the same row (F ^j ) and of different columns (C ^j ) of the same series (S ^j ),

- the distance (DL2 ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) and the same column (C ^j ), said column (C ^j ) being the closest to either the third edge (9) or the fourth edge (10), with respect to the tube (T ^ijk ) of the same series (Sj) closest to said third edge (9) or fourth edge (10),

- the distance (DG ^j ),

^or between the tubes (T ^ijk ) closest to adjacent series (S ^j ), or

^or between the tube (T ^ijk ) closest to the first edge or the second edge (7, 8) and said first edge or second edge (7, 8) of the heat exchanger (1),

they are parameterized so that:

- the parameterization relating to the rows (F ^j ) optimizes mainly the pressure loss of the heat exchanger (1), and

- the parameterization relative to the columns (C ^j ) optimizes mainly the total effective total transfer area of the heat exchanger (1).

[2] Heat exchanger (1) according to [1], where at least two tubes (T ^ijk ) are in fluid communication, forming at least one coil (R ⁱ ).

[3] Heat exchanger (1) according to [2], comprising a plurality (n ^l ) of coils (R ⁱ ), where:

- each coil (R ⁱ ) comprises a plurality (g) of groups (G ^j ), and

- each group (G ^j ) comprises a plurality (n ^g ) of tubes (T ^ijk ),

where each series (S ^j ) is formed by the same group (G ^j ) of each coil (R ⁱ ), and where:

- the number (nFj) of rows (Fj) of each series (Sj) is the number of tubes (Tijk) comprising each group (Gj), and

- the number (ncjf) of columns (Cj) of each series (Sj) is the number of coils (Ri).

[4] Heat exchanger (1) according to any of [1-3], where the total number of tubes (N) meets the expression:

[5] Heat exchanger (1) according to [3], where the total number of tubes (N) meets the expression:

N = g .nl.ng

[6] Heat exchanger (1) according to any of [1-5], where the total number (N) of tubes (T ^ijk ) of the heat exchanger (1) is obtained from the following relationship:

^{az N c- a} 71 ^{jm = lr mn tube m>}

where A is the total thermal transfer effective area of the heat exchanger (1), Fm is a thermal transfer factor and Atub0 ^{m is} the total thermal transfer area of a tube (T ^ijk ).

[7] Heat exchanger (1) according to any of [1-6], where the distance (DL3 ^jn ) is the distance from the third edge or the fourth edge (9, 10) to the tube (T ^ijk ) closest to each series (S ^j ), this distance being, preferably, the minimum distance established by construction of the heat exchanger (1).

[8] Heat exchanger (1) according to claim 7, wherein the parameterized distances DT ^jf , DL1 ^jfl , DL2 ^jf , DL3 ^jn and DG ^j of said heat exchanger (1) fulfill the following expressions according to the width (B) and the length (L) of the heat exchanger (1):

donde

where

^or L = max ( Lj f) ^{| / = 1} + E ^{£ = 1} DL3jn, Vj = 1, ..., ns

[9] Heat exchanger (1) according to [8], where at least one of the parameterized distances DTjf, DL1jfl, DL2jf, DL3jn and DGj maintains a constant value.

[10] Heat exchanger (1) according to [8] or [9], where all parameterized distances DTjf are equal, all parameterized distances DGj between tubes (Tijk) are equal and the number (nFj) of rows (Fj) of each series (Sj) is the same, and the following is true expression:

B = ( ns 1) DGj ns ( nFj - l) DTjf

[11] Heat exchanger (1) according to any of [8-10], where all parameterized distances DL1jfl are equal, all parameterized distances DL3jn are equal, the number (nFj) of rows (Fj) of each series (Sj) ) is equal and the number (ncjf) of columns (Cj) of each series (Sj) is equal, and where the following expression is fulfilled:

[12] Heat exchanger (1) according to any of [2-11], wherein said heat exchanger (1) comprises:

- two input manifolds (5), and

- two output manifolds (6)

where each of the coils (Ri) is connected alternately to a different input manifold (5) and a different output manifold (6), so that the path of the working fluid has a direction that alternates at each serpentine (Ri).

[13] Heat exchanger (1) according to any of [1-12], where each tube (Tijk) is a circular tube with equal outside diameter (O).

[14] Wind tunnel (2) comprising at least one heat exchanger (1) according to any of [1-13].

[15] Method of temperature regulation of an air flow inside a wind tunnel (2) comprising the following stages:

- providing at least one heat exchanger (1) according to any of [1-13],

- measure the temperature of the air flow inside the wind tunnel (2),

- regulate the temperature of the air flow by modifying the number of tubes (T ^ijk ) of the heat exchanger (1) by means of closing means, or the conditions of the working fluid, or the parameterized distances DT ^jf , DL1 ^jfl , DL2 ^jf and DG ^j .

[16] Design method for designing a heat exchanger (1) for a wind tunnel (2) according to any of [7-13], which comprises the following stages:

- defining the dimensions of the heat exchanger (1), said dimensions being width (B), height (H) and length (L),

- determine the total effective area (A) of heat transfer of the required heat exchanger (1) as well as the heat transfer factor (F ^m ) and the total area (A ^{tube m} ) of heat transfer, of each tube (T ^ijk) ),

- determine the total number (N) of tubes (T ^ijk ) of the heat exchanger (1) by the following expression:

^to _™ Y _j w _{m = l} F _rm A _{n ^ tubom >}

- determine the total number (n ^S ) of series (S ^j ), the total number (n ^Fj ) of rows (F ^j ) of each series (S ^j ), and the total number (n ^Cjf ) of columns (C) ^j ) of each series (S ^j ),

- determine the following parameters:

^or the distance (DT ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) of the same series (S ^j ),

^or the distance (DL1 ^jfl ) between tubes (T ^ijk ) of the same row (F ^j ) and of different columns (C ^j ) of the same series (S ^j ),

^or the distance (DL2 ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) and the same column (C ^j ), said column (C ^j ) being the closest either to the third edge (9) or to the fourth edge (10), with respect to the tube (T ^ijk ) of the same series (S ^j ) closest to said third edge (9) or fourth edge (10),

^or the distance (DGj),

■ between the nearest tubes (Tijk) of adjacent series (Sj), or

■ between the tube (Tijk) closest to the first edge or the second edge (7, 8) and said first edge or second edge (7, 8) of the heat exchanger (1),

^or the distance (DL3jn) of the third edge or fourth edge (9, 10) to the tube (Tijk) closest to each series (Sj)

according to the following expressions:

o Ljf = [( ^{Z "= Cf} 1 DLljf ^ DL2 ^jf] , Vf ^{= 1,} ... ^, nFj ^and Vj = ^1, ... ^, ns

or L = max {L] f) ^{| / = 1 Z ^ = 1} DL3jn, Vj = 1, ..., ns

[17] Design method for designing a heat exchanger (1) according to [16], which further comprises the step of determining the total number (nl) of coils (Ri), the number (g) of groups (Gj) and the number (ng) of tubes (Tijk) in each group (Gj), prior to the step of determining the different parameters DTjf, DL1jfl, DL2jf, DL3jn and DGj.

Claims (17)

1. Heat exchanger (1) for wind tunnels (2), comprising: - at least one first wall (3) and a second wall (4), each wall (3, 4) comprising at least one first edge (7), a second edge (8), a third edge (9) and a fourth edge (10), - a total number (N) of tubes (T ^ijk ) adapted to contain a working fluid, forming at least a plurality of said tubes (T ^ijk ) at least one series (S ^j ), the total number being (n ^S ) of series (S ^j ), - at least one inlet manifold (5) of the working fluid connected to a first end of at least one tube (T ^ijk ), and - at least one outlet manifold (6) of the working fluid connected to a second end of at least one tube (T ^ijk ), wherein the tubes (T ^ijk ) of each series (S ^j ) form a plurality (n ^Fj ) of rows (F ^j ) and a plurality (n ^cjf ) of columns (C ^j ) distributed according to the rows (F ^j ), and where: - the distance (DT ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) of the same series (S ^j ), - the distance (DL1 ^jfl ) between tubes (T ^ijk ) of the same row (F ^j ) and of different columns (C ^j ) of the same series (S ^j ), - the distance (DL2 ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) and the same column (C ^j ), said column (C ^j ) being the closest to either the third edge (9) or the fourth edge (10), with respect to the tube (T ^ijk ) of the same series (Sj) closest to said third edge (9) or fourth edge (10), - the distance (DG ^j ), ^or between the tubes (T ^ijk ) closest to adjacent series (S ^j ), or ^or between the tube (T ^ijk ) closest to the first edge or the second edge (7, 8) and said first edge or second edge (7, 8) of the heat exchanger (1), they are parameterized so that: - distance (DL2jf)> 0, and - distance (DGj)> distance (DTjf), so that: - the parameterization relative to the rows (Fj) optimizes mainly the loss of pressure of the heat exchanger (1), and - the parameterization relating to the columns (Cj) optimizes mainly the total effective total transfer area of the heat exchanger (1). 2. Heat exchanger (1) according to claim 1, wherein at least two tubes (Tijk) are in fluidic communication, forming at least one coil (Ri). 3. Heat exchanger (1) according to claim 2, comprising a plurality (nl) of coils (Ri), where: - each coil (Ri) comprises a plurality (g) of groups (Gj), and - each group (Gj) comprises a plurality (ng) of tubes (Tijk), where each series (Sj) is formed by the same group (Gj) of each coil (Ri), and where: - the number (nFj) of rows (Fj) of each series (Sj) is the number of tubes (Tijk) comprising each group (Gj), and - the number (ncjf) of columns (Cj) of each series (Sj) is the number of coils (Ri). 4. Heat exchanger (1) according to any of the preceding claims, wherein the total number of tubes (N) meets the expression:

5. Heat exchanger (1) according to claim 3, wherein the total number of tubes (N) fulfills the expression: N = g .nl.ng 6. Heat exchanger (1) according to any of the preceding claims, wherein the total number (N) of tubes (Tijk) of the heat exchanger (1) is obtained in the following relationship: ^{a j} 71 ^{N c- a Jm = l r mn tube m>} where A is the total thermal transfer effective area of the heat exchanger (1), Fm is a thermal transfer factor and Atub0 ^{m is} the total thermal transfer area of a tube (Tijk). 7. Heat exchanger (1) according to any of the preceding claims, wherein the distance (DL3jn) is the distance from the third edge or the fourth edge (9, 10) to the tube (Tijk) closest to each series (Sj), this distance being, preferably, the minimum distance established by construction of the heat exchanger (1). 8. Heat exchanger (1) according to claim 7, wherein the parameterized distances DTjf, DL1jfl, DL2jf, DL3jn and DGj of said heat exchanger (1) fulfill the following expressions according to width (B) and length (L) of the heat exchanger (1):

9. Heat exchanger (1) according to claim 8, wherein at least one of the parameterized distances DTjf, DL1jfl, DL2jf, DL3jn and DGj maintains a constant value. Heat exchanger (1) according to claim 8 or 9, where all the parameterized distances DTjf are equal, all the parameterized distances DGj between tubes (Tijk) are equal and the number (nFj) of rows (Fj) of each series (Sj) is the same, and the following expression is fulfilled: B = ( ns 1) DGj ns ( nFj - l) DTjf 11. Heat exchanger (1) according to any of claims 8 to 10, wherein all the parameterized distances DL1jfl are equal, all parameterized distances DL3jn are equal, the number (nFj) of rows (Fj) of each series (Sj) is equal and the number (ncjf) of columns (Cj) of each series (Sj) is equal, and where the following expression is fulfilled:

12. Heat exchanger (1) according to any of claims 2 to 11, wherein said heat exchanger (1) comprises: - two input manifolds (5), and - two outlet manifolds (6) where each of the coils (Ri) is connected alternately to a different input manifold (5) and a different output manifold (6), so that the path of the working fluid has a direction that alternates at each serpentine (Ri). 13. Heat exchanger (1) according to any of the preceding claims, wherein each tube (Tijk) is a circular tube with equal outside diameter (O). 14. Wind tunnel (2) comprising at least one heat exchanger (1) according to any of the preceding claims. 15. Method of temperature regulation of an air flow inside a wind tunnel (2) comprising the following stages: - providing at least one heat exchanger (1) according to any of claims 1 to 13, - measure the temperature of the air flow inside the wind tunnel (2), - regulating the temperature of the air flow by modifying the number of tubes (Tijk) operative of the heat exchanger (1) by means of closing means, or conditions of the working fluid, or the parameterized distances DTjf, DL1jfl, DL2jf and DGj. 16. Design method for designing a heat exchanger (1) for a wind tunnel (2) according to any of claims 7 to 13, comprising the following steps: - defining the dimensions of the heat exchanger (1), said dimensions being width (B), height (H) and length (L), - determine the total effective area (A) of heat transfer of the required heat exchanger (1) as well as the thermal transfer factor (Fm) and the total area (Atubo m) of thermal transfer, of each tube (Tijk), - determine the total number (N) of tubes (Tijk) of the heat exchanger (1) by the following expression:

- determine the total number (n ^S ) of series (S ^j ), the total number (n ^Fj ) of rows (F ^j ) of each series (S ^j ), and the total number (n ^Cjf ) of columns (C) ^j ) of each series (S ^j ), - determine the following parameters: ^or the distance (DT ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) of the same series (S ^j ), ^or the distance (DL1 ^jfl ) between tubes (T ^ijk ) of the same row (F ^j ) and of different columns (C ^j ) of the same series (S ^j ), ^or the distance (DL2 ^jf ) between tubes (T ^ijk ) of different rows (F ^j ) and the same column (C ^j ), said column (C ^j ) being the closest either to the third edge (9) or to the fourth edge (10), with respect to the tube (T ^ijk ) of the same series (S ^j ) closest to said third edge (9) or fourth edge (10), ^or the distance (DG ^j ), ■ between the tubes (T ^ijk ) closest to adjacent series (S ^j ), or ■ between the tube (T ^ijk ) closest to the first edge or the second edge (7, 8) and said first edge or second edge (7, 8) of the heat exchanger (1), ^or the distance (DL3 ^jn ) of the third edge or fourth edge (9, 10) to the tube (T ^ijk ) closest to each series (S ^j ) according to the following expressions:

17. Design method for designing a heat exchanger (1) according to claim 16, further comprising the step of determining the total number (n ^l ) of coils (R ⁱ ), the number (g) of groups (G ^j) ) and the number (n ^g ) of tubes (T ^ijk ) in each group (G ^j ), prior to the stage of determining the different parameters DT ^jf , DL1 ^jfl , DL2 ^jf , DL3 ^jn and DG ^j .